The most expensive mistake in lawn seeding isn’t buying cheap seed — it’s using the rate for the wrong grass. A pound of Kentucky bluegrass holds roughly 1.4 million seeds; a pound of tall fescue holds about 230,000. That seed-size gap is why the same 1,000 square feet needs just 2–3 lb of bluegrass but 8–10 lb of fescue, and why the “coverage” number on the bag can mislead you badly if it assumes a different species than you’re sowing.
This calculator uses university extension rates for ten common grasses — cool-season types like bluegrass, the fescues, and perennial rye, and warm-season types like Bermuda, Zoysia, and centipede. Pick your grass and your project: new lawns over bare soil get the full rate, overseeding a thin lawn takes half, because existing turf out-competes much of what you sow. You’ll get total pounds, the published range behind the number, a germination timeline so you know when to stop holding your breath (rye shows in 5 days; bluegrass can take a month), and the right seeding window for your grass type — late summer for cool-season, late spring for warm-season. More seed is not a better lawn; the right seed at the right rate is.
Frequently Asked Questions
How much grass seed do I need per 1,000 square feet?
It depends on the species. New-lawn rates per 1,000 square feet: Kentucky bluegrass 2–3 lb, tall fescue 8–10 lb, perennial ryegrass 6–9 lb, fine fescue 4–5 lb, Bermudagrass 1–2 lb, Zoysia 1–2 lb, centipede just 0.25–0.5 lb. The 20-fold spread comes from seed size — smaller-seeded species pack far more seeds into each pound.
How much seed for overseeding compared to a new lawn?
Use about half the new-lawn rate. Existing turf shades and out-competes new seedlings, so a full rate is wasted — for tall fescue that means 4–5 lb per 1,000 square feet instead of 8–10. Mow the lawn short and rake or core-aerate first so seed reaches soil; seed sitting on a thatch layer rarely establishes.
When is the best time to plant grass seed?
Cool-season grasses (bluegrass, fescues, ryegrass) establish best from late summer to early fall — about 6–8 weeks before the first frost, when soil is warm but air is cooling and weed pressure fades. Warm-season grasses (Bermuda, Zoysia, centipede, Bahia) need soil at 65°F or warmer, so seed them in late spring to early summer after the last frost.
How long does grass seed take to germinate?
Perennial ryegrass is the sprinter at 5–10 days. Tall fescue takes 7–12 days, fine fescue 7–14. Kentucky bluegrass is the slow one — 14–30 days, which surprises many first-time seeders into watering less just when it matters most. Warm-season species generally need 10–30 days plus warm soil. Keep the top half-inch of soil evenly moist the entire time.
What happens if I use too much grass seed?
Seedlings sown too thick compete for light, water, and nitrogen, stay spindly, and become prone to damping-off fungus — the stand usually thins itself back to a normal density anyway, so the extra seed buys disease risk rather than thicker turf. Put the money into quality instead: germination above 85% and weed seed below 0.5% on the label.